David Cameron will today seek to redefine the special relationship between the United States and Britain, saying he is “hard-headed and realistic”, but not an “idealistic dreamer” about it.

The Prime Minister, who flew to Washington last night for talks with President Barack Obama, described himself as “unapologetically pro-America”, saying he “loved” the US and “what it's done for the world”.

But he called for a more grown-up approach to the way the much vaunted relationship is analysed, saying the “Kremlinology” about just how special it is belongs to another era.

“I care about the depth of our partnership, not the length of our phone calls,” he said. “I hope that in the coming years we can focus on the substance, not endlessly fret about the form.”

Mr Cameron's remarks will be seen as an attempt to escape the microscopic scrutiny which bedevilled his predecessor. Gordon Brown distanced himself from Tony Blair's close relationship with George W Bush but was the subject of hostile media coverage when he tried to forge a close bond with President Obama.

Today Mr Cameron is to spend about three hours at the White House. After an hour of private talks and a working lunch with officials, there will be a “media opportunity” with the President, but Cameron aides said yesterday its precise form was still being “nailed down”.

Writing in the Wall Street Journal today, the Prime Minister said: “No other international alliance seems to come under the intense scrutiny reserved for the one |between Britain and the United States. There is a seemingly endless British preoccupation with the health of the special relationship. I have never understood this anxiety.”

Mr Cameron argued: “The US-UK relationship is simple: it's strong because it delivers for both of us. The alliance is not sustained by our historical ties or blind loyalty. This is a partnership of choice that serves our national interests.”

Describing the partnership as “entirely natural”, he said: “Yes, it always needs care and attention, but it is resilient because it is rooted in strong foundations.”

The Prime Minister said three kinds of critics seemed to fret incessantly about the relationship — those who question the whole concept, those who say it is no longer “special”, and those fixated on form rather than substance. Each is misguided, he claimed.

Mr Cameron said the US is a global power and is strengthening its ties with the world's rising powers. Britain is doing the same thing and he would visit Turkey and India shortly.